Projection screens mounted by brackets so that the screen hangs away from the wall or chalkboard are commonly found in classrooms. In addition to use with photographic slides, these screens are often used to enlarge an image projected from an overhead projector. Most often, the overhead projector sits on a table such that the image is projected at an upward angle onto a vertically-hanging screen. This results in a "keystone" effect where the image is larger at the top of the screen than at the bottom of the screen and therefore is not entirely in focus. The "keystone" effect can be prevented by securing the bottom of the projection screen to the wall so that the plane of the screen is at a right angle to the line of projection. A simple string or chain can be used, but in cases where the projection screen is raised by an electric motor controlled by an automatic shut-off switch, the motor can be burned out if activated without unfastening the string or chain. A rubber band also could be used with the advantage that if the motor is activated without unfastening the rubber band, it will stretch and finally break, therefore preventing motor burn out. However, rubber bands are also unsatisfactory due to the varying size and strength.
It is therefore a primary objective of the present invention to provide an anchoring device that will simply and easily secure the bottom end of a projection screen to the wall so that when the projection screen is raised by an electric motor, the motor cannot be burned out.
It is a further object of the present invention to provide an anchoring device which magnetically secures the bottom end of a projection screen to the wall.
It is a further object of the present invention to provide a projection screen anchoring device that is easy to use, safe in operation, and economical to manufacture.